Heat treatment and manufacture of woven screens.



I No Drawing.

of the bars,

UNITED. STATES PATENT. current.

'WINFIELD S. POTTER, 01F PITTSBURGH, PENNSYLVANIA.

HEAT TREATMENT AND MANUFACTURE OF WOVEN SCREENS.

To all whom it may concern:

Be it known that I,'W1NF1ELD S. POTTER, a citizen of the United States,residing at Pittsburgh, Allegheny county, State of Pennsylvania, haveinvented certain new and useful Improvements in Heat Treatment andManufacture of Woven Screens; and I do hereby declare the following tobe a full, clear, and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same.

The present invention relates to the manufacture of woven steel screens,that is to say, screens which are formed by the interweaving of crossingbars, rods, or wires, of steel, such as ordinary carbon steel, ormanganese steel. The material employed in such manufacture is in theform of rolled bars, coils of rod, or coils of wire, and, in order tofacilitate theinterweaving, the material is appropriately crimped' atthe intersection rods or wires,'in making up the screens. The bars androds are obtained by rolling from relatively large billets, and the wireis obtained by a similar rolling, succeeded by wire drawing. The barsand rods so rolled and the wire so rolled and wire drawn, containserious rolling strains and other hardening andstifiening-characteristics due to the rolling operation, supplemented,inthe case of wire by like effects due to the wire drawing operation.

Inasmuch as carbon steel in a hardened condition is not available forscreen making, for the reason that it would not withstand crimping andweaving in that state, it is customary to employ either a very 'softsteel of low carbon content, or an annealed steel of medium carboncontent, and the annealing efi'ected at a sutliciently hightemperature-to remove, in part at least the more serious rollingstrains, but it is not of a character to remove such segregation ofcarbids as has occurred in the steel.

The crimping operation is effected either in a press, as, for instance,by making a number of crimps by one motion of the press, or in acontinuous manner through is frequently crimping rolls of the generalcharacter of spur gears, and the bending or crimping is ordinarily donewhile the bar or rod is cold. In either case, the bar is not embraced orpressed upon at points-between the crimps, but is indented and offset onthe concave Specification of Letters Patent.

Patented Jan. 16, 1917.

Application filed May 12, 1914. Serial No. 838,029.

bended points or sections of the bar, the

steel is severely strained. Furthermore, in weaving the bars, thestrained sections rep resent the point of greatest wear and also thepoint of most severe strain and shock in service. The load of fallingmaterials to be screened, striking heavily upon these high points of thescreen, and constantly bumping them during service has the effect ofwearing the bar at the crimps, both on their upper and under.sides,onthe upper side tion of the cross-wires, even when as much as one-half ofthe original cross-section of the bar remains, so that the screens aremore often discarded because a number of their cross-bars are brokenthan because of the actual wearing through of the bars. In order toobviate these difiiculties, and particularly to produce woven screens ofhigh quality from high carbon steel, manganese steel, or the like, Isubject the bar, coil of rod, or coil of wire, to a reheating operationat such-a temperature as will remove rolling strains, hardness andstiffness, and I prolong the heating operation for a suflicient periodto remove segregation, that is to say, to take into solution and fullydistribute throughout the steel any carbids that have segregatedtherein. The effect of this heating operation, however, is tore'crystallize and enlarge the granular structure of the steel, andthereby weaken it. Accordingly, I break down the large crystals andregrain the steel at the same time causing the particles of theregrained steel to firmly cohere. This effect of the combined regrainingand increased cohes1on, I produce either by immediately crimping the baror rod while it is still at the temperature to which it has been raisedto remove the rolling strains and to restore the carbids into solution;or, if the crimping is to be effected at a subsequent period, I lightlywork the rod or bar. In the latter case, the light working willordinarily be sufficient-if the lll ' Preferably, however,

preferable to heat the rod or reduction effected by it is'brought aboutby passing it through two roll passes in each of which the bar isreduced say 2% to 5% in cross section. The bar resulting from thisoperation will have a fine grain, strong grain cohesion, an absence ofsegregation, and an absence of the strains, stiffness and hardnessreferred to. Where the bar or rod is crimped immediately after theheating operation, the working of the steel necessary to break down theenlarged grains and regrain it is effected by the crimping operationitself, the crimping, in such case, being effected in a closed roll passso that the bar or rod will be worked throughout; or the bar is passedthrough the crimping rolls and also through a pass at right anglesimmediately preceding the crimping pass. After the light reduction abovereferred to, the bar or rod may be tended screen has large openings andthe rod: does not have to be sharply crimped. it is hot-crimped, and, ifnecessary, it is reheated before the hotcrimping, so as to bring it to asuitable temperature to eliminate any possible strains that may havebeen-introduced by the light rolling, and to lessen the strains due tocrimping. So also, after the hot-crimping, it may be heat-treated, in asuitable furnace, to relieve whatever strains or other irregularities ofcondition troduced during the hot-crimping operation; or, if permittedto cool after hotcrimping, it may be r'e-heated and then heat-treated ata temperature sufficient to bring the steel to the condition required inthe product. A suitable temperature for crimping the rod or. bar,without straining, would be, in the case of carbon steels, as low as 5O0O.;:for manganese steel, it would be bar,- for hot crimping, to atemperature of about 900 C.

The heat treatment, after the hot-crimping operation is for the purposeof imparting to the steel a uniform grain structure appropriate to itsintimate use. In the case of carbon steel of low carbon content, thiseffected by ordinary an may be sufficiently nealing. In the case of barsof carbon steel I having a carbon content higher than that ordinarilyemployed for screen-making, the hot-crimped bar will have sufficientductility or weaving ifgiven the heat-treatment ordinarily called oil,tempering and annealing, consisting of heating a bar to above the carbonsteel critical range, oil-quenching or otherwise say 550 C., orthereabout, and slowly cooling. In the case of manganese steel, theheat-treatment will consist in heating the manganese steel bar or rod;to above the critical point ordinarily located at about 825 C. to 850C,and prolonging the heat cold-crimped and especially this may be donewhen the in that may have been in-v crimped bar, rod,'or wire,

rapidly cooling, heating to quenching.

In accordance with the foregoing description, it will be noted that thesequence of operations after the preliminary heating and re-rolling maybe varied within a considerable range, according to the .choice of theoperator, which would be determined by the quality of the result whichhe desires, the kind and analysis of the -steel and the particularcharacter of the crimping operation itself. Thus, in some instances, itwill be found that crimped immediately after the light reductionreferred to. In other instances, where hot-crimping is practised, thebar or rod may be re-heated either prior to or subsequent to, thehot-crimping or both before and-after the hot-crimping; and, in stillother instances, the final heat-treatment after hot crimping may takeplace without reof the finishing temperature (or any suit able lowertemperature), followed by cooling steps, the desired condition of theproduct.

1. The method of producing from a rolled steel bar, rod, or wire, acorrespondlng crimped bar, rod, or wire, for woven screens, whichcomprises heating the rolled bar, rod, or wire, to such a temperature asto relieve the strains incident to the rolling operation and to bringinto solidsolution in the metal such carbidsas may have segregatedtherein, working the bar, rod, or wire, sufficiently to condense andrefine any coarsely regrained portions thereof and ultimately crimpingit.

2. The method of producing from a rolled steel bar, rod, or wire, acorresponding for woven screens, which comprises heating the rolled bar,rod, or wire, to such a temperature as to relieve thestrains incident tothe rolling operation and to bring into solid solution in the metal suchcarbids as may have segregated therein, working the bar, rod, or wiresufficiently to condense and refine any coarsely regrained portionsthereof and ultimately crimping it, the working being incidental to thecrimping. V-

3. The method of producing from a rolled steel bar, rod, or wire, acorresponding crimped bar, rod, or wire, for woven screens, whichcomprises heating therolled bar, rod, or wire, to such a temperature asto relieve the strains incident to the rolling operation and to bringinto solid solution in the metal the bar or rod may be cold suchconstituents as may have segregated therein, Working the bar, rod orwire sufficiently to condense and refine any coarsely regrained portionsthereof, and ultimately crimping it while still hot, and subsequentlyheat-treating the metal to bring it to the deand to bring into solidsolution in the metal which comprises such constituents as'may havesegregated therein, working the bar, rod or wire sufiiciently tocondense and refine any coarsely regrained portions thereof, andultimately crimping it while still hot, and subsequently heat-treatingthe metal to bring it to the desired final condition, the heat-treatmentbeing preceded by a reheating operation.

5. The method of producing from a rolled steel bar, rod, or wire, acorresponding .crimped'bar, rod, or wire, for woven screens, heating therolled bar, rod,

or wire, to such a temperature as to relieve the strains lncldent to therolling operation and to bring into solid solutionin the metal suchconstituents as may havesegregated therein, working the bar, rod, orw1re suificiently to condense and refine any coarsely regrained portionsthereof, and ultimately crimping it while still hot, and subsequentlyheat-treating the metal to bring it to the desired final condition, ingpreceded by a reheatin'g'operation.

6. The method of producing from a rolled steel bar, rod, or wire, acorresponding crimped bar, rod, or wire, for woven screens, whichcomprises heating the rolled bar, rod,

the strains incident to the rolling operation and to bring into solidsolution in the metal such constituents as may have segregated therein,working the bar, rod, or w1re suificiently to condense and refine anycoarsely regrained portions thereof and ultimately hot-crimping it,subsequently heat-treating the metal to bring it to the desired finalcondition, and re-heating it both before and after the hot-crimping.

In testimony whereof I aflix my signature, in presence of two witnesses.

. WINFIELD S. POTTER. Witnesses:

JOHN C. PENNIE,

K. R. PENN-m.

or wire, to such a temperature as to relieve 35 the hot crimping be- 1

